Oxygenators, which substitute for a patient's lungs during, e.g., open heart surgery, have long been known. Conventionally, such oxygenators work by flowing the patient's blood across a bundle of hollow microporous fibers. Oxygen is pumped through the interior of the fibers, and a gas exchange takes place along the surface of the fibers. Just like in a living lung, oxygen migrates from the fiber interior into the blood, and carbon dioxide migrates from the blood into the fibers.
One problem with currently known oxygenators is that they are vastly less efficient than a natural lung. Conventional oxygenators typically have a blood-oxygen interface surface of about 2 m.sup.2, whereas an adult human lung has an interface surface of about 70 m.sup.2. With pure oxygen and an anesthetized, perfectly still patient, the 2 m.sup.2 surface is sufficient, but it could not sustain life in ordinary air or in an active patient.
Sufferers from emphysema or other lung-damaging diseases would be greatly helped if it were possible to produce an implantable artificial lung with sufficient gas-blood interface area to allow the patient to function in a normal environment. The current fiber technology is not suitable for this purpose because it would require a fiber bundle so large that it could not be implanted and would require an inordinate amount of blood to prime. Consequently, an entirely new departure is needed in the art to create an artificial lung of manageable size yet with an interface surface area approximating that of a natural lung.
The reason why a natural lung has so much interface surface area is that the natural lung is composed of millions of microscopic generally spherical air-containing alveolar sacs whose membrane-like walls are perfused with capillaries through which the blood flows. Imitating that structure with artificially manufactured devices is not practical.